Air bag device

Abstract: An air bag device (10) is comprising a first air bag (11) accommodated in a steering pad and receiving an occupant by the inflation and deployment during a collision and a second air bag (12) seamed with a portion of said first air bag (11) and being inflatable in a ring shape to cover a surface of a steering wheel (2) facing to the occupant, wherein said first air bag (11) and said second air bag (12) having gas communicating holes (20) at a seaming portion between them, said first air bag (11) being inflated by introducing gas from gas generating means (5) connected to a gas inlet of said first air bag and said second air bag (12) being inflated at the same time by introducing gas through said gas communicating holes (20). In a second embodiment, the second air bag is inflated by introducing gas from gas generating means connected to a gas inlet of the second air bag and the first air bag is inflated at the same time by introducing gas through the gas communicating holes. In a third embodiment, gas generating means are connected to a gas inlet of the first air bag and to a gas inlet of the second air bag separately and the two bags are inflated by introducing gas through the separate gas paths from the gas generating means at the same time.

Description: BACKGROUND OF THE INVENTION The present invention relates to an air bag device, more particularly, to an air bag device which can prevent an occupant from bumping against a steering wheel, absorb an impact force applied to the occupant's head and chest and reliably protect the occupant. Recently, an air bag device is adopted to various kinds of vehicles as a passive occupant protection system for efficiently protecting an occupant from the action of the impact force at a collision. The purpose of the air bag device is to prevent the occupant from a secondary collision in a cabin by receiving the occupant's body, particularly, the head and chest with a bag shaped cushion filled with gas during a collision. As shown in Fig. 1, a position D1 of an occupant in a driver's seat moves to the position D2 at a collision, the occupant is protected by being pushed to the deployed air bag 54 at his chest and head. Thereby, the occupant is protected from the secondary collision, that is, the occupant plunges into and bumps against a steering wheel or a windshield of the vehicle. As shown in Fig. 2 (a), an air bag device is proposed wherein the air bag device has a conventional air bag (hereinafter, the air bag shown by an alternate long and short dash line is called by "main bag") and an air bag formed in a ring shape to cover a periphery of the steering wheel (hereinafter, the air bag formed in a ring shape and disposed a periphery of the main bag is called by "sub bag") and both air bags are deployed (See Journal of Technical Disclosure published by Japan Institute of Invention and Innovation, Technical Disclosure No. 88-15251, Published Unexamined Utility model No. 1989-122349). In the air bag device disclosed in the Journal of Technical Disclosure No. 88-15251, as shown in Fig. 2(a) and Fig. 2(b), the sub bag 61 is folded and accommodated in a hollow rim 62 of the steering wheel 70 and gas for inflation and deployment is introduced into the sub bag 61 through a spoke 63 acting also as a gas pipe as shown by the arrow. The hollow rim 62 has a tear line 64 is formed at a predetermined position thereof. As the gas is introduced into the sub bag 61 to apply an inner pressure, the tear line 64 breaks and portions 62a of the hollow rim 62 is expanded in a direction of the arrow B, then the sub bag 61 accommodated inside the hollow rim 62 expands like a rush. At the same time, the main bag 66 expands and deploys so as to prevent the occupant moving in a direction of the arrow A from bumping against the steering wheel 70 and to protect the occupant's head and chest from an impact. However, a considerable capacity in the hollow rim 62 is necessary for folding and accommodating the sub bag 61 in the hollow rim of the steering wheel 70. The diameter of the rim 62 becomes wide, thereby the grip size becomes big and an operational feeling for steering becomes inferior. Because the rim 62 is a portion which the driver always holds to steer, the rim 62 should have rigidity and strength not to break even if the rim is gripped hard. On the other hand, the tear line formed on the periphery of the rim 62 should be formed as a weak part to easily break when the internal pressure is applied by introducing gas. Actually, it is quite difficult to make such a rim 62 structured to be compatible as mentioned above. Furthermore, even if the rim is designed to overcome the conditions, it takes many man-hours to fold and accommodate the sub bag 61 in the rim 62 and to mount the gas pipe and the like. Therefore, the whole air bag device becomes quite expensive. DE-A-22 48 393 discloses an air bag device showing the features mentioned in the preamble of present claim 1. Thus, an air bag device is described which is accommodated in a steering pad and comprises first and second air bags seamed together. The second air bag covers the steering pad and extends around the outer lower surface of the first air bag. This arrangement is not completely satisfactory with regard to the security and production of the air bag device. It is an object of the invention to provide an air bag device which can be produced easily and at reasonable cost, has a simple structure and provides high security to the occupant. The above object is solved with the air bag device according to claim 1. The invention provides an air bag device accommodated in a steering pad comprising:a first air bag receiving an occupant by the inflation and deployment during a collision; and a second air bag seemed with a portion of said first air bag, and being inflatable in a ring shape to cover a surface of a steering wheel facing to the occupant, said second air bag having gas communicating holes to communicate gas with said first air bag, said second air bag being inflated by introducing gas from gas generating means connected to a gas inlet of said second air bag and said first air bag being inflated at the same time by introducing gas through the gas communicating holes. According to the invention, the second air bag is accommodated in the first air bag. According to the above mentioned invention, the air bag device comprises a first air bag receiving an occupant by the inflation and deployment during a collision, and a second air bag seemed with a portion of the first air bag and being inflatable in a ring shape to cover a surface of a steering wheel facing to the occupant so that the air bag device can prevent the occupant form bumping against the steering wheel by the second air bag and can protect the occupant's head and chest by the first air bag. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view showing an operational condition of an air bag device during a collision; Fig. 2 (a) is an explanatory view showing an example of deployment condition of an air bag device having a bag portion for protecting a conventional steering wheel; Fig. 2 (b) is detailed sectional view of the steering wheel as shown in Fig. 2 (a); Fig. 3 is a sectional view showing an embodiment of the air bag according to the invention; and Fig. 4 is a plan sectional view showing an arrangement of gas communicating holes and vent holes which are formed in the air bag device as shown in Fig .3. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The description will now be made as regard to an embodiment which is suitable for explaining an air bag device according to the invention as mentioned above. Fig. 3 is a sectional view showing an example of an air bag device according to an embodiment of the invention. The steering center pad 1 is fixed to an end of a steering column 3 and integrally structured with a steering wheel 2 through spokes (not shown) at a substantially central portion of the steering wheel 2. The steering center pad 1 rotates with the steering wheel 2 around the steering column 3 during steering. A retainer plate is fixed in the steering center pad 1 by a fixing screw (not shown). The retainer plate is for fixedly supporting an inflator 5 as a gas source of the air bag device in the center pad 1. The inflator 5 is an equivalent with one of a conventional air bag device. The inflator 5 has a gas outlet 5a formed in a side surface of a rough flat cylindrical shaped body thereof to spout reaction gas from the gas outlet 5a to inflate and deploy a folded air bag 10 (will be described in detail) in a predetermined shape. The description will be made as regard to the air bag 10 of the air bag device according to the present invention referring to Fig. 3 and Fig. 4. The air bag 10 according to the present invention comprises a main bag 11 as a first air bag and a sub bag 28 as a second air bag fixed to a portion of the main bag 11 and deploying in a ring shape at a position to cover the steering wheel 2 (hereinafter, the main bag and the sub bag are generically called the air bag 10). A nylon fabric of which an inner surface is coated by a silicone is employed as clothes for the main bag 11 and the sub bag 28. The nylon woven fabric is a fabric woven with fine threads of approximately 420 deniers so that the folded size of the air bag 10 is smaller. In this embodiment, the main bag 11 and the sub bag 28 are inflated simultaneously with the reaction gas generated from the single inflator 5. Gas communicating holes 20 are provided in the connecting portion between the main bag 11 and the sub bag 28 as shown in Fig. 4. Thereby, the reaction gas spouted from the inflator 5 inflates the main bag 11 and the sub bag. The volume of the sub bag 28 is pretty smaller than one of the main bag 11. Each diameter of the gas communicating holes 20 of the sub bag 28 and main bag 11 is set in a suitable size to properly set for the inflation timing of the both bags. Though the number of the gas communicating holes 20 provided at a rough cross position centered the gas inlet 28a of the main bag 11 is four in this embodiment, the diameter and the number of the gas communicating holes may be freely chosen. At this stage, the number of the gas communicating holes 20 is preferably from two to four to inflate the sub bag at a uniform pace. In this embodiment, two vent holes 27 are provided near the gas inlet 28a of the main bag 11. The vent holes 27 exhaust gas in the main bag 11 gradually when the occupant strongly bumps into the inflated main bag 11. Thereby, the main bag 11 has a long buffer stroke so as to absorb an impact applied to the occupant's face or the like when the occupant bumps into the main bag 11. In this manner, the gas in the main bag is exhausted through the vent holes 27 while the occupant bumps into the air bag so that the main bag 11 can absorb the impact and protect the occupant. In other words, if the main bag 11 has no gas outlet hole such as the vent holes 27, the occupant tends to strongly rebound off the main bag 11 when the occupant collides with the main bag 11. Such a phenomenon is called a rebound phenomenon. If the rebound phenomenon of the air bag is severe, the air bag cannot work its function as an impact absorbing device. On the other hand, it is an object of the sub bag 28 to prevent the occupant from directly bumping against the steering wheel 2. Therefore, the sub bag 28 may not be provided with a measure for easing the rebound phenomenon. Because the sub bag normally has no vent hole, the sub bag is maintained the inflation condition in a rough ring shape with high internal pressure. The description will be made with regard to the structure of the steering center pad in which the air bag is accommodated. In one embodiment, the steering center pad 1 has a lid. The lid may be a resin molding product produced by molding urethane resin on a surface of an aluminum plate as a core of the resin molding product. Though a tear line is provided at a substantial central portion of the lid of the pad 1 facing the occupant, the lid is maintained its stiffness not to break by a normal horn operation and a light contact. On the other hand, as the reaction gas is introduced into the main bag 11 at a collision, the main bag 11 is inflated slightly to push the lid from the inside thereof. When the internal pressure is over the predetermined threshold, the tear line provided in the inner surface of the lid breaks so that the air bag 10 folded inside rushes out. In the air bag device of the invention described in Fig. 3 and 4, the sub bag 28 has a gas inlet 28a to communicate the gas between the sub bag 28 and the main bag 11. A base portion 28B of the sub bag 28 is accommodated in the steering center pad 1. The gas inlet 28a provided in the base portion 28B connects with the inflator 5 at the lower side of the pad and maintains the airtightness. Furthermore, a sub bag gas path 26 formed in a rough cross shape is provided by seaming with the main bag 11 as shown in Fig. 4. The sub bag 28 is supplied with gas from the inflator 5 through the sub bag gas path 26. On the other hand, a peripheral edge of the base panel 28B is seamed with a ring panel 28A made of a ring shaped cloth. Four pores as shown in Fig. 4 are provided in the ring panel 28A. The pores are gas communicating holes 20 to the main bag 11 to introduce the gas supplied in the sub bag 28 to the main bag 11 to inflate the main bag 11. Vent holes 27 are provided out of the portion of the sub bag gas path 26. The vent holes 27 have the function described hereinbefore. According to this embodiment, the gas is introduced from the inflator 5 to inflate the sub bag 28 and into the main bag 11 through the gas communicating holes 20 to inflate the main bag 11 at substantially the same time. Therefore, the pressure in the sub bag 28 can be maintained higher than the pressure in the main bag 11. The sub bag 28 can prevent the occupant more reliably from colliding with the steering wheel. The base panel 28B of sub bag 28 is accommodated in the main bag 11 and the gas communicating holes are independently provided in the surface of a ring panel 28A accommodated in the main bag 11 so that the gas communicating holes are not seamed with the textile of the main bag 11 as shown in Fig. 3 in this embodiment. The structure as mentioned above can simplify a cutting form of the cloth for each bag and reduce the seaming portions thereby increase the productivity of the air bag. The volume of the main bag is increased because the sub bag 28 is accommodated in the main bag 11 in this embodiment. The capacity of the gas generation of the inflator is preferable to be set suitably. It is a secondary effect that the receiving area of the main bag 11 is wider. As apparent from the above description, the air bag device according to the invention can prevent the occupant from colliding with the steering wheel by means for reasonable cost and effectively acts the occupant protection function as an essential function of the air bag.

Claims: An air bag device accommodated in a steering pad (1) comprising: a first air bag (11) receiving an occupant by the inflation and deployment during a collision; and a second air bag (28) seamed with a portion of said first air bag, and being inflatable in a ring shape to cover a surface of a steering wheel (2) facing to the occupant, said second air bag having gas communicating holes (20) to communicate gas with said first air bag, said second air bag being inflated by introducing gas from gas generating means (5) connected to a gas inlet (28a, 26) of said second air bag and said first air bag being inflated at the same time by introducing gas through said gas communicating holes (20), characterized in that said second air bag (28) is accommodated in said first air bag (11).

Inventors: FUJII HIROAKI, OSADA NOBUYA, TAKEDA HIDEO, YAMANISHI TAKAHIRO, FUJII, HIROAKI, OSADA, NOBUYA, TAKEDA, HIDEO, YAMANISHI, TAKAHIRO
Applicants: TAKATA CORP, TAKATA CORPORATION
Application year: 1994
Main classification: B60R21
IPC codes: B60R21